Test stand for testing hydraulic devices

Abstract

A test stand for testing hydraulic devices such as hydraulic pumps and motors, either separately or jointly. The test stand is comprised of a primary power source which acts in combination with a hydraulic motor to drive a drive train, which is in turn, operated by a hydraulic pump. The hydraulic pump and the hydraulic motor are fluidly connected together by passage means so that hydraulic fluid can be pumped therebetween. A pressure control means is present in the passage means for sensing and preventing the pressure from going above a predetermined value. Connected between this pressure control means and the hydraulic motor is a control means for adjusting the fluid displacement of the hydraulic motor to correspond to the fluid output of the hydraulic pump. This control means enables the hydraulic motor to operate in synch with the hydraulic pump at all times. The test stand also has power regenerative features wherein the hydraulic motor is capable of converting the fluid pressure to mechanical power. This power is then used to drive the drive train.

We claim: 
     
       1. A test stand for testing hydraulic devices such as hydraulic pumps and motors, either separately or jointly, said test stand comprising: (a) a primary power source;   (b) a hydraulic motor;   (c) a hydraulic pump;   (d) a drive train operatively connected to said primary power source, to said hydraulic motor and to said hydraulic pump;   (e) passage means for fluidly connecting said hydraulic pump to said hydraulic motor;   (f) pressure control means for preventing pressure build-up within said passage means above a predetermined value; and   (g) system control means for adjusting fluid displacement of said hydraulic motor to correspond to fluid output of said hydraulic pump, said system control means including a control mechnanism electrically connected to said pressure control means and a composite actuator.   
     
     
       2. The test stand of claim 1 wherein said passage means is a charged closed loop. 
     
     
       3. The test stand of claim 1 wherein said pressure control means is a pressure control valve. 
     
     
       4. The test stand of claim 1 wherein said system control means comprises a pressure-activated control mechanism connected between said pressure control means and said hydraulic motor. 
     
     
       5. A test stand for testing hydraulic devices such as hydraulic pumps and motors, either separately or jointly, said test stand comprising: (a) a primary power source;   (b) a hydraulic motor capable of converting hydraulic power into mechanical power;   (c) a hydraulic pump;   (d) a drive train operatively connected to said primary power source, to said hydraulic motor and to said hydraulic pump;   (e) passage means for fluidly connecting said hydraulic pump to said hydraulic motor in a closed loop, said passage means having a high pressure side and a low pressure side;   (f) charge means for delivering fluid to said low pressure side of said passage means;   (g) pressure control means for preventing build-up of pressure within said high pressure side of said passage means above a predetermined value; and   (h) system control means for adjusting fluid displacement of said hydraulic motor to correspond to fluid output of said hydraulic pump, said system control means including a cylinder containing a spring loaded piston electrically connected to said pressure control means, said piston being in a destroking mode when no signal is received from said pressure control means.   
     
     
       6. The test stand of claim 5 wherein said pressure control means is a pressure control valve. 
     
     
       7. The test stand of claim 6 wherein said pressure control valve is a pressure relief valve. 
     
     
       8. The test stand of claim 5 wherein said system control means comprises a control mechanism connected between said pressure control means and said hydraulic motor. 
     
     
       9. The test stand of claim 8 wherein said control mechanism is a composite actuator. 
     
     
       10. A test stand for testing hydraulic devices, such as hydraulic pumps and motors, either separately or jointly, said test stand comprising: (a) a primary power source;   (b) a variable displacement hydraulic motor capable of converting hydraulic power into mechanical power;   (c) a drive train drivingly connected to both said primary power source and to said variable displacement hydraulic motor;   (d) a variable displacement hydraulic pump drivingly operated by said drive train;   (e) passage means for fluidly connecting said hydraulic pump to said hydraulic motor;   (f) pressure control means for preventing build-up of pressure within said passage means above a predetermined value; and   (g) system control means for adjusting fluid displacement of said hydraulic motor to correspond to fluid output of said hydraulic pump, said system control means including a composite actuator and a cylinder containing a spring loaded piston electrically connected to said pressure control means, said piston being in a destroking mode when no signal is received from said pressure control means and being in a stroking mode when a signal is received from said pressure control means.   
     
     
       11. A test stand for testing hydraulic pumps and motors, either separately or jointly, wherein said hydraulic pump or motor or both are the test items, said test stand comprising: (a) a primary power source;   (b) a variable displacement hydraulic motor capable of converting hydraulic power into mechanical power;   (c) a drive train drivingly connected to both said primary power source and to said variable displacement hydraulic motor;   (d) a fixed displacement hydraulic pump drivingly operated by said drive train;   (e) passage means for fluidly connecting said hydraulic pump to said hydraulic motor in a closed loop, said passage means having a high pressure side and a low pressure side;   (f) charge means for delivering fluid to said low pressure side of said passage means;   (g) pressure control means for preventing build-up of pressure within said high pressure side of said passage means above a predetermined value; and   (h) system control means for adjusting fluid displacement of said hydraulic motor to correspond to fluid output of said hydraulic pump, said system control means including a composite actuator and a cylinder containing a spring loaded piston electrically connected to said pressure control means, said piston being in a destroking mode when no signal is received from said pressure control means and being in a stroking mode when a signal is received from said pressure control means.